This invention relates generally to trailers and more particularly to an anti-sway hitch assembly used for coupling a trailer to a tow vehicle.
Automobiles and pick-up trucks long have been used to tow trailers such as utility trailers, camping trailers and boat trailers. Typically, the trailer is connected to the tow vehicle through a ball and socket coupling located at the rear of the tow vehicle. More specifically, the tow vehicle is fitted with a hitch ball which projects upwardly in the region of the rear bumper of the vehicle, while the trailer has a socket coupler on a forward projecting tongue, the socket firing over and closing around the hitch ball to secure the trailer to the tow vehicle. The ball and socket arrangement allows the tow trailer to turn relative to the tow vehicle so that the combination is maneuverable. However, Such a ball and socket collection also allows the trailer to rock forwardly and rearwardly with respect to the tow vehicle, and also rock left and right with respect to the tow vehicle.
The offset of the hitch from the rear axle of the tow vehicle detracts from the overall stability of the combination, particularly at higher speeds, for it enables and induced forces to cause a swaying motion known as fishtailing. The wind simply may be surface winds or gusts of winds produced by a storm. The wind may also be generated by large vehicles, such as an over-the-road truck, traveling at a high rate of speed. Such vehicles can create wind turbulence that affects any other vehicle which happens to be along side of it. Inertial forces created by uneven road surfaces may also produce fishtailing.
Irrespective of its source, fishtailing is dangerous because it may cause the driver of the tow vehicle to lose control of the vehicle. Moreover, fishtailing imposes severe stresses on the trailer hitch and the frame components to which it is attached. Fishtailing likewise imposes severe demands on the suspension system of the tow vehicle, and may cause components such as shock absorbers, bushings and springs to experience excessive wear or to fail.
While large over-the road tractor-trailer combinations would appear to be more susceptible to fishtailing, they are not. This derives from the fact that the pivot axis for the trailer is set generally over the rear axle of the tractor. In vehicles with tandem rear axles, the pivot mechanism or fifth wheel, as it is called, often is located over the space between the two axles. In any event, tractor-trailer combinations do not pivot substantially behind the rear axle or axles of the tractor and, therefore, these combinations possess good stability at high speeds.
Generally, most devices previously known for reducing swaying and fishtailing had the effect of stiffening the pivot joints. They are not very effective and impose substantial stresses on the vehicular components, particularly when turns are negotiated. Other devices, such as the hitch disclosed in U.S. Pat. No. 4,019,754 function by shifting the effective pivot point forward. However, that hitch mechanism does not accommodate sharp turns of the type one may encounter when attempting to park a trailer in a confined parking space or when navigating on city streets.
My trailer hitch assembly, disclosed in U.S. Pat. No. 4,722,542, provides a trailer hitch which allows a trailer to be towed without significant swaying or fishing tailing by effectively placing the pivot axis forwardly of its location and while being capable of accommodating sharp turns. Although my previous trailer hitch works well for its intend purposes, it sometimes exhibits limited applications. For example, the hitch works exceedingly well in larger, heavier trailers, for example camping trailers. These larger camping trailers generally employ their own brakes, usually electric brakes associated with the trailer wheels that are simultaneously actuated when the driver actuates the tow vehicle brakes.
Smaller or lighter weight trailers, such as boat trailers or other light-duty trailers, generally are equipped with a surge brake mechanism. Basically, the surge brake works through a hydraulic system wherein a master cylinder in the coupler or socket housing located on the trailer tongue is actuated by forward movement of the trailer against the hitch ball. This forward motion applies a brake to the trailer wheels in response to the force of the trailer against the tow vehicle as the trailer surges forward when the tow vehicle slows. Surge brake assemblies have been used to control lateral movement, i.e. fishtailing. For example, U.S. Pat. No. 3,948,544 discloses hydraulic surge brakes that operate the right trailer brake in response to lateral forces to the left and operates the left trailer brake in response to lateral forces to the left.
It subsequently became apparent that my anti-way trailer hitch, as disclosed in the U.S. Pat. No. 4,722,542 does not work well in combination with a conventional surge brake system. Since my trailer hitch so effectively controls unwanted side-to-side and forward and rearward movement of the trailer, there is little or no movement to actuate a surge brake mechanism employed by the trailer.
Further, in trailer and tow vehicle combinations that allow some forward or rearward movement of the trailer relative to the tow vehicle, there are significant stresses placed on the hitch. In conventional trailer hitches, the forward or rearward stresses are concentrated on the hitch bar attached to the tow vehicle. Further, as the tow vehicle moves forward and backward there are significant push-pull forces on the trailer hitch. Conventional hitch bars are constructed to accommodate such stresses. However, in a hitch employing my novel converging links mechanism much of the forward or rearward stress is applied to the converging links mechanism. Forward pressure on the converging links can cause undesired side-to-side movement or folding of the links with a trailer having no brakes or surge brake. Moreover, such force could cause premature wear of the converging links assemblies. It would be advantageous, therefore, to have a trailer hitch employing converging links mechanism that prevents fish-tailing yet could be used on a light weight trailer employing surge brakes. Furthermore, it also would be advantageous to have a hitch assembly in which the forward or rearward stresses would be borne by the hitch box, hitch bar or other strut and not the converging links mechanism.